The specific goal of the present study was to establish lymphnode metastasis system(s) using C3H/HeJ mouse tumors and to investigate irradiation effect on metastatic development to lymphnodes. Mouse tumor systems of spontaneous origin named NFSA2ALM1 fibrosarcoma and NR-S1 squamous cell carcinoma were inoculated in the footpad of a hind leg. Metastatic lymphnode enlargement (confirmed by histology) was detected by about 2 weeks after the tumor cell inoculation, while clonogenic tumor cell release into the blood circulation started around 10 days and macroscopic lung nodules developed after 3-4 weeks of the tumor cell inoculation.Local tumor irradiatioon was found to suppress lymphnode metastatic development dose-dependently between 10 and 40 Gy.These results support and extend the conclusion of the previous study regarding 1) suppressive effect of local tumor irradiaiton on the clonogenic tumor cell release (CTCR) into the blood circulation and on the metastatic development to the lung, and 2) CTCR effeciency may predict the metastatic efficiency, i.e. high CTCR correlates to high spontaneous metastasis efficiency to the lung or lymphnodes.2)平成4年度にかけて、局所腫瘍への照射の影響について、血中への游出及び肺転移とリンパ節転移とでの違いの可能性も含め研究を進めた。移植7日目の腫瘍部照射により、10-40Gyの範囲で調べたところ、線量依存性にリンパ節転移数も抑制されることが判明した。また、リンパ節部を含む前照射によって、リンパ節転移が増加することもなかった。3)これらの結果は、肺への血行転移や血中への腫瘍細胞の游出と同様、リンパ節転移についても、腫瘍局所照射は転移抑制的に作用することを示し、従来からの研究成果で示唆されている腫瘍細胞の血中への游出能の実験測定が転移能を予測できるという仮説を支持する。